diff --git a/src/stores/login.ts b/src/stores/login.ts
index 9327050..dbd1ee6 100644
--- a/src/stores/login.ts
+++ b/src/stores/login.ts
@@ -17,7 +17,7 @@ export default defineStore('loginStore', {
     userData: {},
     isLoggedIn: false,
     rememberedReturnToUrl: "",
-    expired: new Date().setMonth(6), // 設定 Refresh Token 的到期日為半年後
+    expired: (() => { const d = new Date(); d.setMonth(d.getMonth() + 6); return d.getTime(); })(), // 設定 Refresh Token 的到期日為半年後
   }),
   actions: {
     /**
diff --git a/tests/stores/login.test.js b/tests/stores/login.test.js
index 03eace7..2055336 100644
--- a/tests/stores/login.test.js
+++ b/tests/stores/login.test.js
@@ -143,4 +143,17 @@ describe('loginStore', () => {
     store.setIsLoggedIn(true);
     expect(store.isLoggedIn).toBe(true);
   });
+
+  describe('expired', () => {
+    it('is approximately 6 months in the future', () => {
+      const now = new Date();
+      const sixMonthsLater = new Date(now);
+      sixMonthsLater.setMonth(sixMonthsLater.getMonth() + 6);
+
+      const expiredDate = new Date(store.expired);
+      // Allow 1 day tolerance
+      const diffMs = Math.abs(expiredDate.getTime() - sixMonthsLater.getTime());
+      expect(diffMs).toBeLessThan(24 * 60 * 60 * 1000);
+    });
+  });
 });